Air conditioning system for vehicle

ABSTRACT

An air conditioning system for a vehicle is provided with a heat pump circulation path through which a refrigerant body is circulated through a compressor. The heat pump circulation path is provided with a condenser unit, an expansion valve, a first evaporator, a heater, and a second evaporator. The heat pump circulation path is also provided with a bypass means which, in heating operation, bypasses a main condenser for constituting the condenser unit and connects the heater and a gas-liquid separation-type refrigerant body containing section. The configuration provides effects which minimize an increase in the number of dedicated parts required only in a heating mode and which, by effectively utilizing the system in a cooling mode, prevents a reduction in the air conditioning performance caused by the shortage of the refrigerant body.

TECHNICAL FIELD

The present invention relates to a vehicular air conditioning systemincorporated in a vehicle for air-conditioning a passenger cabin of thevehicle.

BACKGROUND ART

Vehicles, e.g., engine automobiles having an internal combustion engine,hybrid automobiles having an engine and a secondary battery (or asecondary battery and a fuel cell or the like) in combination, electricautomobiles, and fuel cell automobiles, incorporate various types ofvehicular air conditioning systems.

For example, as shown in FIG. 19, a vehicular air conditioningapparatus, as disclosed in Japanese Laid-Open Patent Publication No.2009-023564, includes a compressor 1 for drawing in and discharging arefrigerant, a condenser 3 disposed in an air conditioning unit case 2for heating air through heat exchange between the air and therefrigerant that is discharged from the compressor 1 in a heating mode,a receiver 4 for receiving the refrigerant flowing in from the condenser3 and performing gas-liquid separation in the heating mode, asupercooler 5 for supercooling the liquid refrigerant that flows in fromthe receiver 4 through heat exchange between the liquid refrigerant andambient air in the heating mode, a depressurizer 6 for depressurizingthe refrigerant that has been supercooled by the supercooler 5 in theheating mode, and an outdoor heat exchanger 7 for evaporating therefrigerant depressurized by the depressurizer 6 in the heating mode.

With the above vehicular air conditioning apparatus, subcooling (i.e., adegree of subcooling) is achieved by the receiver 4, and further isadditionally achieved reliably by the supercooler 5, which is disposeddownstream of the receiver 4, using ambient air in the heating mode. Thevehicular air conditioning apparatus is rendered highly efficient andexcellent in heating performance through a relatively simple cyclicarrangement.

According to Japanese Laid-Open Patent Publication No. 2009-023564, thereceiver 4 and the supercooler 5 are used only in the heating mode, andthus, the receiver 4 and the supercooler 5 are not required in a coolingmode. Therefore, the number of components dedicated to the heating modeis increased, which makes the vehicular air conditioning apparatusuneconomical.

According to Japanese Laid-Open Patent Publication No. 2009-023564,furthermore, the vehicular air conditioning apparatus does not include abuffer in order to make up for a refrigerant shortage in the case thatthe cooled liquid refrigerant remains trapped in the outdoor heatexchanger 7, and the amount of refrigerant used for air-conditioning thevehicle is reduced in the cooling mode. Consequently, air-conditioningperformance is lowered due to the refrigerant shortage, resulting in theneed for a power increase caused by a capability shortage of thecompressor 1, and also resulting in poor mileage on account of the powerincrease.

SUMMARY OF INVENTION

The present invention has been made in order to solve the aforementionedproblems. It is an object of the present invention to provide avehicular air conditioning system, which is capable of increasing heatexchange efficiency and maintaining good air-conditioning performance asa result of stably circulating a refrigerant by means of a simple andeconomical arrangement.

According to the present invention, there is provided a vehicular airconditioning system of the heat pump type comprising a condenser forperforming heat exchange between a refrigerant and ambient air, thecondenser being connected to a heat pump circulation path forcirculating the refrigerant with a compressor, an evaporator connectedto the heat pump circulation path for performing heat exchange betweenthe refrigerant and air-conditioning air, and a heater connected to theheat pump circulation path for performing heat exchange between therefrigerant which has been delivered from the compressor and theair-conditioning air that has passed through the evaporator.

The air conditioning system further comprises a gas-liquid separationrefrigerant storage unit, a supercooling heat exchanger, and a bypassmeans connecting the gas-liquid separation refrigerant storage unit andthe supercooling heat exchanger downstream of the heater in bypassingrelation to the condenser in a heating mode.

According to the present invention, the gas-liquid separationrefrigerant storage unit functions as a buffer for making up orcompensating for a refrigerant shortage in a cooling mode. Therefore,when the air conditioning system operates in the heating mode at anincreased ambient air temperature, as well as when the air conditioningsystem operates in a transient mode such as a dehumidifying heatingmode, no refrigerant shortage occurs, thereby allowing the airconditioning system to perform air-conditioning in a stable manner.

In the heating mode, the heater, the gas-liquid separation refrigerantstorage unit, and the supercooling heat exchanger are connected inbypassing relation to the condenser. Consequently, the gas-liquidseparation refrigerant storage unit functions as a subcooling tank. As aresult, liquid refrigerant, which is produced upon separation of gascontained in the refrigerant, flows through the supercooling heatexchanger (subcooling condenser) and is cooled to an ambient airtemperature range. Accordingly, there is no need to provide a subcoolingtank and a subcooler, which would be used only in the heating mode.

It is thus possible to increase heat exchange efficiency and to maintaingood air-conditioning performance by stably circulating the refrigerantby means of a simple and economical arrangement.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram of a vehicular air conditioningsystem according to a first embodiment of the present invention;

FIG. 2 is a schematic view showing the manner in which the vehicular airconditioning system operates in a heating mode;

FIG. 3 is a diagram showing a cycle on a Mollier chart plotted when thevehicular air conditioning system operates in the heating mode;

FIG. 4 is a schematic view showing the manner in which the vehicular airconditioning system operates in a dehumidifying heating mode;

FIG. 5 is a schematic view showing the manner in which the vehicular airconditioning system operates in a cooling mode;

FIG. 6 is a schematic block diagram of a vehicular air conditioningsystem according to a second embodiment of the present invention;

FIG. 7 is a diagram showing a cycle on a Mollier chart plotted when thevehicular air conditioning system operates in a heating mode;

FIG. 8 is a schematic block diagram of a vehicular air conditioningsystem according to a third embodiment of the present invention;

FIG. 9 is a schematic block diagram of a vehicular air conditioningsystem according to a fourth embodiment of the present invention;

FIG. 10 is a schematic view showing the manner in which the vehicularair conditioning system operates in a heating mode;

FIG. 11 is a schematic view showing the manner in which the vehicularair conditioning system operates in a dehumidifying heating mode;

FIG. 12 is a schematic view showing the manner in which the vehicularair conditioning system operates in a cooling mode;

FIG. 13 is a schematic block diagram of a vehicular air conditioningsystem according to a fifth embodiment of the present invention;

FIG. 14 is a schematic view showing the manner in which the vehicularair conditioning system operates in a cooling mode;

FIG. 15 is a schematic block diagram of a vehicular air conditioningsystem according to a sixth embodiment of the present invention;

FIG. 16 is a schematic view showing the manner in which the vehicularair conditioning system operates in a cooling mode;

FIG. 17 is a schematic block diagram of a vehicular air conditioningsystem according to a seventh embodiment of the present invention;

FIG. 18 is a schematic block diagram of a vehicular air conditioningsystem according to an eighth embodiment of the present invention; and

FIG. 19 is a diagram illustrating the vehicular air conditioningapparatus disclosed in Japanese Laid-Open Patent Publication No.2009-023564.

DESCRIPTION OF EMBODIMENTS

As shown in FIGS. 1 and 2, a vehicular air conditioning system 10according to a first embodiment of the present invention is incorporatedin an automobile (vehicle) 12 for air-conditioning a passenger cabin(vehicle compartment) 14 of the automobile 12.

The air conditioning system 10 has a heat pump circulation path 18 forcirculating a refrigerant via a compressor 16. The heat pump circulationpath 18 includes therein a condenser unit (condenser) 20 for performingheat exchange between the refrigerant and ambient air, an expansionvalve 22 for depressurizing the refrigerant delivered from the condenserunit 20, a first evaporator (evaporator) for performing heat exchangebetween the refrigerant that has passed through the expansion valve 22and air-conditioning air, and a heater 26 for performing heat exchangebetween the refrigerant delivered from the compressor 16 and theair-conditioning air that has passed through the first evaporator 24.

The heat pump circulation path 18 branches into a branch path 28, whichincludes a second evaporator (rear evaporator) 30 for performing heatexchange between a heat medium discharged from the cabin 14 (waste heatgas from the cabin 14) and the refrigerant.

Since the heating medium used for heat exchange in the second evaporator30 is an exhaust heat gas from the cabin 14, heat that is carried in thecabin 14 can effectively be utilized without being abandoned. When theair conditioning system 10 is activated for warming the cabin 14, heatused to warm the cabin 14 is retrieved and introduced again into the airconditioning system 10. Therefore, the air conditioning system 10 can bestarted up quickly.

The condenser unit 20 includes a main condenser (condensing device) 32,a gas-liquid separation refrigerant storage unit (subcooling tank) 34,and a subcondenser (supercooling heat exchanger) 36, which are connectedmutually in series downstream of the heater 26, and through which therefrigerant flows in a cooling mode. A solenoid-operated valve 38 a isdisposed upstream of the main condenser 32.

A bypass means 40 is connected to the heat pump circulation path 18 forconnecting the heater 26 to the gas-liquid separation refrigerantstorage unit 34 and the subcondenser 36 in bypassing relation to themain condenser 32 in a heating mode. The bypass means 40 includes afirst bypass path 42 a, which branches from the heat pump circulationpath 18 and is connected to the gas-liquid separation refrigerantstorage unit 34 of the condenser unit 20. The first bypass path 42 aincludes a solenoid-operated valve 38 b.

The expansion valve 22 includes a means (not shown) for detecting thetemperature of the refrigerant delivered from the first evaporator 24,which cools the air-conditioning air. An opening of the expansion valve22 is variable automatically depending on the temperature of therefrigerant delivered from the first evaporator 24, for thereby varyingthe flow rate of the refrigerant.

The heat pump circulation path 18 also includes a three-way valve 44 aat a junction between a portion of a path near the expansion valve 22and an inlet of the branch path 28. The heat pump circulation path 18further includes a three-way valve 44 b at a junction between an outletof a second bypass path 42 b, which bypasses the first evaporator 24,and the heat pump circulation path 18. The second evaporator 30 isdisposed in a rear portion of the automobile 12 (see FIG. 2).

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Between the first evaporator 24 and the heater 26, there is disposed anair mixing damper 46 for introducing air-conditioning air, having beencooled by the first evaporator 24, into the cabin 14 in bypassingrelation to the heater 26.

The automobile 12 has an ambient air inlet 48 for introducing ambientair as the air-conditioning air. The first evaporator 24 and the heater26 are successively disposed in this order downstream of the ambient airinlet 48. The air conditioning system 10 includes a controller (ECU) 50,which functions as a flow path switching means, for controlling thesolenoid-operated valves 38 a, 38 b and the three-way valves 44 a, 44 bto switch between the heating mode and the cooling mode, and which alsocontrols the air conditioning system 10 in its entirety (see FIG. 1).

Operations of the air conditioning system 10 will be described belowwith reference to a cycle diagram shown in FIG. 3.

When the air conditioning system 10 operates in a heating mode, as shownin FIG. 2, the compressor 16 is actuated to deliver refrigerant into theheat pump circulation path 18. The refrigerant is supplied to the heater26, which carries out heat exchange between the refrigerant and theair-conditioning air (radiates heat into the air-conditioning air) inorder to increase the temperature of the air-conditioning air.

The solenoid-operated valve 38 a is closed and the solenoid-operatedvalve 38 b is opened, so as to allow the refrigerant, which isdischarged from the heater 26, to pass through the first bypass path 42a and directly into the gas-liquid separation refrigerant storage unit34, in bypassing relation to the main condenser 32. The refrigerantflows from the gas-liquid separation refrigerant storage unit 34 throughthe subcondenser 36. The subcondenser 36 cools the refrigerant anddelivers the cooled refrigerant to the expansion valve 22.

The refrigerant is depressurized by the expansion valve 22 and branchesthrough the three-way valve 44 a into the branch path 28, from which therefrigerant is introduced into the second evaporator 30. The secondevaporator 30 carries out heat exchange between the refrigerant and aheat source in the cabin 14. The refrigerant then bypasses the firstevaporator 24 and flows back into the compressor through the secondbypass path 42 b and the expansion valve 22.

According to the first embodiment, the main condenser 32, the gas-liquidseparation refrigerant storage unit 34, and the subcondenser 36 areconnected mutually in series downstream of the heater 26. The heat pumpcirculation path 18 includes the bypass means 40, which connects theheater 26 to the gas-liquid separation refrigerant storage unit 34 andthe subcondenser 36, in bypassing relation to the main condenser 32 inthe heating mode.

When the air conditioning system 10 operates in the heating mode, asshown in FIG. 2, a portion of the heat pump circulation path 18downstream of the heater 26 is connected to the gas-liquid separationrefrigerant storage unit 34 and the subcondenser 36 in bypassingrelation to the main condenser 32. The gas-liquid separation refrigerantstorage unit 34 and the subcondenser thus function respectively assubcooling tanks (see the gas-liquid separation refrigerant storage unit34 and the subcondenser 36 in FIG. 3).

The refrigerant can thus be introduced as a perfect liquid medium intothe expansion valve 22, whereby the expansion valve 22 is effectivelyprevented from trapping gas therein. Therefore, the heat pumpcirculation path 18 is capable of stably circulating the refrigerant,thereby easily increasing air-conditioning performance and maintainingthe air-conditioning performance favorably.

The gas-liquid separation refrigerant storage unit 34 is used as asubcooling tank. Consequently, the gas-liquid separation refrigerantstorage unit 34 can provide a sufficient amount of refrigerant, makingit possible to prevent air-conditioning performance from being lowereddue to a shortage of refrigerant when the air conditioning system 10operates in the heating mode at an increased ambient air temperature, aswell as when the air conditioning system 10 operates in a transient modesuch as a dehumidifying heating mode.

According to the first embodiment, furthermore, there is no need toprovide a subcooling tank and a subcooler for use only in the heatingmode, because the gas-liquid separation refrigerant storage unit 34 andthe subcondenser 36 of the condenser unit 20, which as described laterserves as a heat radiator in the cooling mode, can be shared with theheating mode. Since there are no devices that are used only in theheating mode, the system installation space in the front portion of thevehicle that incorporates the air conditioning system 10 therein iseffectively reduced.

Consequently, by stably circulating the refrigerant with a simple andeconomical arrangement, it is possible to increase the heat exchangeefficiency and to maintain good air-conditioning performance.

Operations of the air conditioning system 10 in the dehumidifyingheating mode will be described below.

When the air conditioning system 10 operates in the dehumidifyingheating mode, as shown in FIG. 4, the three-way valve 44 b is actuatedin order to close the second bypass path 42 b, thereby connecting thefirst evaporator 24 to the heat pump circulation path 18. When thecompressor 16 is operated, the refrigerant delivered into the heat pumpcirculation path 18 flows through the heater 26, which radiates heatfrom the refrigerant. Thereafter, the refrigerant flows through thegas-liquid separation refrigerant storage unit 34, the subcondenser 36,and the expansion valve 22, whereupon the refrigerant becomes lower inpressure and temperature. The heat of the refrigerant is absorbed by thesecond evaporator 30 and thereafter the refrigerant is delivered to thefirst evaporator 24.

The first evaporator 24 absorbs heat from the air-conditioning airthereby cooling the air-conditioning air. Thereafter, the temperature ofthe air-conditioning air is increased by the heater 26 and theair-conditioning air is then introduced into the cabin 14. Since theair-conditioning air is cooled by the first evaporator 24, water vaporcontained in air that is introduced from outside the automobile 12 isremoved, i.e., the introduced air is dehumidified.

Even if the air-conditioning air that passes through the firstevaporator 24 is low in temperature, the second evaporator 30 absorbs asufficient amount of heat from a heat source that is discharged from thecabin 14, which is high in temperature and low in humidity, therebyheating the refrigerant that flows into the first evaporator 24.Therefore, even when the air conditioning system operates in thedehumidifying heating mode, the second evaporator 30 does not freeze andis capable of operating continuously.

Since the refrigerant is supplied to the gas-liquid separationrefrigerant storage unit 34, the gas-liquid separation refrigerantstorage unit 34 also functions as a subcooling tank. As a result, whenthe refrigerant is distributed at the time that the air conditioningsystem 10 operates in a transient mode such as the dehumidifying heatingmode, no shortage of refrigerant occurs, thus allowing the airconditioning system 10 to operate with stable air-conditioningperformance.

FIG. 5 shows the manner in which the vehicular air conditioning system10 operates in the cooling mode.

When the air conditioning system 10 is operated in the cooling mode, thesolenoid-operated valve 38 a is opened and the solenoid-operated valve38 b is closed, whereby the condenser unit 20 is connected to the heatpump circulation path 18. The three-way valves 44 a, 44 b are switchedin order to disconnect the branch path 28 from the heat pump circulationpath 18, and to connect the first evaporator 24 to the heat pumpcirculation path 18. The air mixing damper 46 remains fully closed.

The compressor 16 is actuated in order to compress the refrigerant to ahigh temperature. Compressed refrigerant flows through the heater 26 andthen the refrigerant is cooled by the condenser unit 20. Thereafter, therefrigerant is converted by the expansion valve 22 into a refrigerant oflow temperature and low pressure, whereupon the refrigerant is suppliedto the first evaporator 24. When the low-temperature refrigerant flowsthrough the first evaporator 24, the first evaporator 24 carries outheat exchange between the refrigerant and the air-conditioning air. Theair-conditioning air is cooled, and the refrigerant flows from theexpansion valve 22 back into the compressor 16 after heat from therefrigerant is absorbed by the expansion valve 22.

The air-conditioning air, which has been cooled by the first evaporator24, is not heated since the air mixing damper 46 is closed, and theair-conditioning air is introduced into the cabin 14, thereby coolingthe cabin 14. In the cooling mode, the gas-liquid separation refrigerantstorage unit 34 performs a dampening action so as to dampen any increaseor decrease in the amount of refrigerant.

FIG. 6 is a schematic block diagram of a vehicular air conditioningsystem 60 according to a second embodiment of the present invention.Parts of the air conditioning system 60 according to the secondembodiment, which are identical to those of the air conditioning system10 according to the first embodiment, are denoted by identical referencecharacters, and such features will not be described in detail below.Similarly, parts of air conditioning systems according tolater-described third through eighth embodiments of the presentinvention, which are identical to those of the air conditioning system10 according to the first embodiment, are denoted by identical referencecharacters, and such features will not be described in detail below.

The air conditioning system 60 includes a bypass means 62 connected tothe heat pump circulation path 18, for thereby connecting the heater 26to the gas-liquid separation refrigerant storage unit 34 in bypassingrelation to the main condenser 32 in the heating mode. The bypass means62 includes the first bypass path 42 a and a flow rate control valve 64,for example, a metering valve, a flow rate regulating valve, or thelike, which is connected to the first bypass path 42 a and serves as apressure loss device for causing the refrigerant to undergo a pressureloss. An opening of the flow rate control valve 64 is adjusted by anactuator such as a motor 66, for example.

According to the second embodiment, as shown in a cycle diagramillustrated in FIG. 7, since the flow rate control valve 64 is used as apressure loss device, the subcooling region in the heating mode can beincreased. Therefore, when the ambient temperature is very low, the flowrate control valve 64 can be actuated to increase the enthalpydifference at the heater 26.

In addition, with such an increased amount of subcooling, the respectiveinlet temperatures of the gas-liquid separation refrigerant storage unit34 and the subcondenser 36, which serves as a supercooling heatexchanger, can be lowered to a temperature equivalent to that of thevery low ambient temperature. Therefore, heat radiation from ambient airin the supercooling heat exchanger can be held to a minimum.

Furthermore, since the amount of subcooling is increased, the capacityof the heater 26 can be increased to a higher temperature and/or higherpressure (from pressure a to pressure al). The heating performance ofthe heater 26 can thus be effectively increased.

FIG. 8 is a schematic block diagram of a vehicular air conditioningsystem 70 according to a third embodiment of the present invention.

The air conditioning system 70 includes a bypass means 72, which isconnected to the heat pump circulation path 18, for connecting theheater 26 to the gas-liquid separation refrigerant storage unit 34 inbypassing relation to the main condenser 32 in the heating mode. Thebypass means 72 includes the first bypass path 42 a and a capillary 74,which is connected to the first bypass path 42 a and serves as apressure loss device for causing the refrigerant to undergo a pressureloss. The solenoid-operated valve 38 b is connected upstream of thecapillary 74.

According to the third embodiment, since the capillary 74 is used as apressure loss device, the same advantages as those of the secondembodiment are achieved. For example, the subcooling region in theheating mode can be increased.

FIG. 9 is a schematic block diagram of a vehicular air conditioningsystem 80 according to a fourth embodiment of the present invention.FIG. 10 is a schematic diagram of the vehicular air conditioning system80.

The air conditioning system 80 includes a condenser 82 connected to theheat pump circulation path 18 for performing heat exchange between therefrigerant and the ambient air, and a bypass means 84 connected to theheat pump circulation path 18 for connecting the heater 26 to thegas-liquid separation refrigerant storage unit 34 and the subcondenser36 in bypassing relation to the condenser 82 in the heating mode.

The condenser 82 comprises a condensing device 86, a tank 88, and asupercooler 90, which are coupled together integrally. Thesolenoid-operated valve 38 a is connected between the condenser 82 andthe heater 26 and is positioned close to an upstream end of thecondenser 82.

The bypass means 84 includes the first bypass path 42 a, in which thereare included the gas-liquid separation refrigerant storage unit 34, thesubcondenser 36, and the solenoid-operated valve 38 b.

The air conditioning system 80 operates in the same manner as shown inthe cycle diagram of FIG. 3. More specifically, when the airconditioning system 80 is operated in the heating mode, as shown in FIG.10, the compressor 16 is actuated in order to deliver refrigerant intothe heat pump circulation path 18. The refrigerant is supplied to theheater 26, which carries out heat exchange between the refrigerant andthe air-conditioning air (i.e., radiates heat into the air-conditioningair) so as to increase the temperature of the air-conditioning air.

Then, the solenoid-operated valve 38 a is closed and thesolenoid-operated valve 38 b is opened in order to allow therefrigerant, having been discharged from the heater 26, to pass throughthe first bypass path 42 a directly into the gas-liquid separationrefrigerant storage unit 34 in bypassing relation to the condenser 82.The refrigerant flows from the gas-liquid separation refrigerant storageunit 34 and through the subcondenser 36, which cools the refrigerant anddelivers the cooled refrigerant to the expansion valve 22.

According to the fourth embodiment, the gas-liquid separationrefrigerant storage unit 34 and the sub-condenser 36 are connectedmutually in series through the first bypass path 42 a downstream of theheater 26. The heat pump circulation path 18 includes the bypass means84, which connects the heater 26 to the gas-liquid separationrefrigerant storage unit 34 and the subcondenser 36, in bypassingrelation to the condenser 82 in the heating mode.

When the air conditioning system 80 is operated in the heating mode, asshown in FIG. 10, a portion of the heat pump circulation path 18downstream of the heater 26 is connected to the gas-liquid separationrefrigerant storage unit 34 and the subcondenser 36 in bypassingrelation to the condenser 82. The gas-liquid separation refrigerantstorage unit 34 thus functions as a subcooling tank. When gas containedin the refrigerant supplied to the gas-liquid separation refrigerantstorage unit 34 is separated from the refrigerant, a liquid refrigerantis produced through operation of the gas-liquid separation refrigerantstorage unit 34. The liquid refrigerant is cooled to an ambienttemperature range when the liquid refrigerant flows through thesubcondenser 36.

The refrigerant can thus be introduced as a perfect liquid medium intothe expansion valve 22, thereby effectively preventing gas from becomingtrapped in the expansion valve 22. Therefore, the heat pump circulationpath 18 is capable of stably circulating the refrigerant, thereby easilyincreasing air-conditioning performance and maintaining theair-conditioning performance favorably.

The gas-liquid separation refrigerant storage unit 34 is used as asubcooling tank. Consequently, the gas-liquid separation refrigerantstorage unit 34 can provide a sufficient amount of refrigerant, thusmaking it possible to prevent air-conditioning performance from beinglowered due to a shortage of refrigerant when the air conditioningsystem 80 operates in the heating mode at an increased ambient airtemperature, as well as when the air conditioning system 80 operates ina transient mode such as a dehumidifying heating mode. Therefore, thefourth embodiment provides the same advantages as those of the firstthrough third embodiments.

Since the subcondenser 36 can be located freely, the layout freedom ofthe air conditioning system 80 is effectively increased. Thesubcondenser 36 may be located in any position insofar as ambient aircan flow through the subcondenser 36. Thus, the subcondenser 36 can beinstalled easily and effectively.

Operations of the air conditioning system 80 in the dehumidifyingheating mode will be described below.

When the air conditioning system 80 is operated in the dehumidifyingheating mode, as shown in FIG. 11, the three-way valve 44 b is actuatedin order to close the second bypass path 42 b and to connect the firstevaporator 24 to the heat pump circulation path 18. When the compressoris operated, the refrigerant, which is delivered into the heat pumpcirculation path 18, flows through the heater 26. Thereafter, therefrigerant flows through the gas-liquid separation refrigerant storageunit 34, the subcondenser 36, and the expansion valve 22, whereupon therefrigerant is lowered in pressure and temperature. Heat of therefrigerant is absorbed by the second evaporator 30, and thereafter, therefrigerant is delivered to the first evaporator 24.

The first evaporator 24 absorbs heat from the air-conditioning air inorder to cool the air-conditioning air. Thereafter, the temperature ofthe air-conditioning air is increased by the heater 26, and then theair-conditioning air is introduced into the cabin 14. Since theair-conditioning air is cooled by the first evaporator 24, water vaporcontained in air that is introduced from outside the automobile 12 isremoved, i.e., the air introduced into the automobile 12 isdehumidified.

FIG. 12 shows the manner in which the vehicular air conditioning system80 operates in the cooling mode.

When the air conditioning system 80 is operated in the cooling mode, thesolenoid-operated valve 38 a is opened and the solenoid-operated valve38 b is closed, thereby connecting the condenser 82 to the heat pumpcirculation path 18. The three-way valves 44 a, 44 b are switched inorder to disconnect the branch path 28 from the heat pump circulationpath 18 and to connect the first evaporator 24 to the heat pumpcirculation path 18. The air mixing damper 46 remains fully closed.

The compressor 16 is actuated in order to compress the refrigerant to ahigh temperature. Compressed refrigerant flows through the heater 26 andthen the refrigerant is cooled by the condenser 82. Thereafter, therefrigerant is converted by the expansion valve 22 into a refrigerant oflow temperature and low pressure, whereupon the refrigerant is suppliedto the first evaporator 24. When the low-temperature refrigerant flowsthrough the first evaporator 24, the first evaporator 24 carries outheat exchange between the refrigerant and the air-conditioning air. Theair-conditioning air is cooled, and the refrigerant flows from theexpansion valve 22 back into the compressor 16 after heat from therefrigerant is absorbed by the expansion valve 22.

The air-conditioning air, which has been cooled by the first evaporator24, is not heated since the air mixing damper 46 is closed. Theair-conditioning air is introduced into the cabin 14, thereby coolingthe cabin 14. In the cooling mode, the gas-liquid separation refrigerantstorage unit 34 performs a dampening action so as to dampen any increaseor decrease in the amount of refrigerant.

FIG. 13 is a schematic block diagram of a vehicular air conditioningsystem 100 according to a fifth embodiment of the present invention.

In the air conditioning system 100, a bypass means 102 is connected tothe heat pump circulation path 18 for connecting the heater 26 to thegas-liquid separation refrigerant storage unit 34 and to thesubcondenser 36 in bypassing relation to the condenser 82 in the heatingmode. The bypass means 102 includes the first bypass path 42 a, which isconnected parallel to the condenser 82 and includes a solenoid-operatedvalve 38 b.

The heat pump circulation path 18 includes the gas-liquid separationrefrigerant storage unit 34 and the subcondenser 36, which arepositioned between the outlet of the condenser 82 and the inlet of theexpansion valve 22.

According to the fifth embodiment, when the air conditioning system 100is operated in the heating mode, as shown in FIG. 13, thesolenoid-operated valve 38 a is closed and the solenoid-operated valve38 b is opened. When the compressor 16 is actuated, refrigerant isdischarged from the heater 26 and flows through the first bypass path 42a directly into the gas-liquid separation refrigerant storage unit 34 inbypassing relation to the condenser 82. The refrigerant flows from thegas-liquid separation refrigerant storage unit 34 and through thesubcondenser 36, which cools the refrigerant and delivers cooledrefrigerant to the expansion valve 22. The gas-liquid separationrefrigerant storage unit 34 thus functions as a subcooling tank. Liquidrefrigerant, which is produced when gas contained in the refrigerant isseparated, flows through the subcondenser 36, thereby producing aperfect liquid medium. Therefore, the heat pump circulation path 18 iscapable of stably circulating the refrigerant therethrough, therebyeasily increasing and maintaining good air-conditioning performance.Therefore, the fifth embodiment provides the same advantages as those ofthe first through fourth embodiments.

When the air conditioning system 100 is operated in the cooling mode, asshown in FIG. 14, the solenoid-operated valve 38 a is opened and thesolenoid-operated valve 38 b is closed while the three-way valves 44 a,44 b are switched. When the compressor 16 is actuated to compress therefrigerant to a high temperature, compressed refrigerant flows throughthe heater 26, and thereafter, the refrigerant is cooled by thecondenser 82. Then, the refrigerant is converted by the subcondenser 36and the expansion valve 22 into a refrigerant of low temperature and lowpressure, whereupon the refrigerant is supplied to the first evaporator24. In the cooling mode, therefore, similar to the heating mode, thegas-liquid separation refrigerant storage unit 34 performs a dampeningaction so as to dampen any increase or decrease in the amount ofrefrigerant.

FIG. 15 is a schematic block diagram of a vehicular air conditioningsystem 110 according to a third embodiment of the present invention.

The air conditioning system 110 includes a bypass means 112 connected tothe heat pump circulation path 18 for connecting the heater 26 to thegas-liquid separation refrigerant storage unit 34 in bypassing relationto the condenser 82 in the heating mode. The bypass means 112 includesthe first bypass path 42 a, which includes the solenoid-operated valve38 b, the gas-liquid separation refrigerant storage unit 34, and thesubcondenser 36. The gas-liquid separation refrigerant storage unit 34and the subcondenser 36 are disposed between the first evaporator 24 andthe heater 26.

According to the sixth embodiment, when the air conditioning system 110is operated in the heating mode, as shown in FIG. 15, thesolenoid-operated valve 38 a is closed and the solenoid-operated valve38 b is opened. When the compressor 16 is actuated, refrigerant isdischarged from the heater 26 and flows through the first bypass path 42a directly into the gas-liquid separation refrigerant storage unit 34 inbypassing relation to the condenser 82. The refrigerant flows from thegas-liquid separation refrigerant storage unit 34 and through thesubcondenser 36, which cools the refrigerant and delivers cooledrefrigerant to the expansion valve 22.

When the air conditioning system 110 is operated in the cooling mode,the solenoid-operated valve 38 a is opened and the solenoid-operatedvalve 38 b is closed while the three-way valves 44 a, 44 b are switched.Upon actuation of the compressor 16 to compress the refrigerant to ahigh temperature, the compressed refrigerant flows through the heater 26and then is cooled by the condenser 82.

According to the sixth embodiment, therefore, the heat pump circulationpath 18 is capable of stably circulating the refrigerant, thereby easilyincreasing and maintaining good air-conditioning performance. Thus, thesixth embodiment provides the same advantages as those of the firstthrough fifth embodiments.

FIG. 17 is a schematic block diagram of a vehicular air conditioningsystem 120 according to a seventh embodiment of the present invention.

The air conditioning system 120 includes a bypass means 122 connected tothe heat pump circulation path 18 for connecting the heater 26 to thegas-liquid separation refrigerant storage unit 34 and the subcondenser36 in bypassing relation to the condenser 82 in the heating mode.

The bypass means 122 includes a flow rate control valve 124, forexample, a metering valve, a flow rate regulating valve, or the like,which is connected to the first bypass path 42 a and serves as apressure loss device for causing the refrigerant to undergo a pressureloss. The opening of the flow rate control valve 124 is adjusted by anactuator such as a motor 126, for example.

According to the sixth embodiment, since the flow rate control valve 124is used as a pressure loss device, in the same manner as the cyclediagram shown in FIG. 7, a subcooling region can be increased in theheating mode. Therefore, when the ambient temperature is very low, theflow rate control valve 64 can be actuated in order to increase theenthalpy difference at the heater 26.

In addition, due to the increased amount of subcooling, the inlettemperature of the gas-liquid separation refrigerant storage unit 34 andthe subcondenser 36, which serves as a supercooling heat exchanger, canbe lowered to a temperature that is equivalent to that of the very lowambient temperature. Therefore, heat radiation from ambient air in thesupercooling heat exchanger can be held to a minimum.

Furthermore, since the amount of subcooling is increased, the capacityof the heater 26 can be increased to a higher temperature and/or higherpressure. The heating performance of the heater 26 can thus beeffectively increased.

In essential features thereof, the seventh embodiment is based on thefourth embodiment. However, the seventh embodiment is not strictlylimited to the fourth embodiment, but may be based on the fifthembodiment or the sixth embodiment. The same also applies to the eighthembodiment, as described below.

FIG. 18 is a schematic block diagram of a vehicular air conditioningsystem 130 according to an eighth embodiment of the present invention.

The air conditioning system 130 includes a bypass means 132 connected tothe heat pump circulation path 18 for connecting the heater 26 to thegas-liquid separation refrigerant storage unit 34 and the subcondenser36 in bypassing relation to the condenser 82 in the heating mode. Thebypass means 72 includes a capillary 134, which is connected to thefirst bypass path 42 a and serves as a pressure loss device for causingthe refrigerant to undergo a pressure loss. The solenoid-operated valve38 b is disposed upstream of the capillary 134, whereas the gas-liquidseparation refrigerant storage unit 34 and the subcondenser 36 aredisposed downstream of the capillary 134.

According to the eighth embodiment, since the capillary 134 is used as apressure loss device, the same advantages as those of the seventhembodiment are achieved. For example, the subcooling region in theheating mode can be increased.

In each of the above embodiments, the heat medium, which undergoes heatexchange with the refrigerant in the second evaporator 30, may be, asidefrom the waste heat gas from the cabin 14, any medium that is higher intemperature than the refrigerant flowing into the second evaporator 30,e.g., a medium carrying heat from the motor, heat from the battery, heatfrom an internal combustion engine assuming the vehicle has an internalcombustion engine, heat from the controller 50, or heat from ambientair, etc.

The three-way valves 44 a, 44 b for switching between flow paths may beformed from a combination of a branch block and a solenoid-operatedvalve for switching between flow paths, instead of an integral assemblyof a three-way branch and a valve mechanism.

1. A vehicular air conditioning system of a heat pump type comprising: acondenser for performing heat exchange between a refrigerant and ambientair, the condenser being connected to a heat pump circulation path forcirculating the refrigerant with a compressor; an evaporator connectedto the heat pump circulation path for performing heat exchange betweenthe refrigerant and air-conditioning air; and a heater connected to theheat pump circulation path for performing heat exchange between therefrigerant, which has been delivered from the compressor, and theair-conditioning air that has passed through the evaporator; thevehicular air conditioning system further comprising: a gas-liquidseparation refrigerant storage unit; a supercooling heat exchanger; andbypass means connecting the gas-liquid separation refrigerant storageunit and the supercooling heat exchanger downstream of the heater inbypassing relation to the condenser in a heating mode.
 2. The vehicularair conditioning system according to claim 1, further comprising: a rearevaporator connected to a branch path, which branches from the heat pumpcirculation path, for performing heat exchange between the refrigerantand a heating medium, which is obtained from inside or outside of avehicle, and which is higher in temperature than the refrigerant.
 3. Thevehicular air conditioning system according to claim 2, wherein theheating medium, which exchanges heat with the refrigerant in the rearevaporator, comprises waste heat gas from a cabin.
 4. The vehicular airconditioning system according to claim 1, further comprising anexpansion valve for depressurizing the refrigerant delivered from thecondenser.
 5. The vehicular air conditioning system according to claim1, wherein the condenser comprises a main condenser, the gas-liquidseparation refrigerant storage unit, and the supercooling heatexchanger, which are connected mutually in series downstream of theheater, and through which the refrigerant flows in a cooling mode. 6.The vehicular air conditioning system according to claim 1, wherein thebypass means comprises a pressure loss device for causing therefrigerant to undergo a pressure loss.